


I'll tell you my sins and you can sharpen your knife

by caranfindel



Category: Supernatural
Genre: Episode AU: s10e14 The Executioner's Song, Episode: s10e14 The Executioner's Song, Gen, Mark of Cain, Post-Episode: s10e14 The Executioner's Song, season 10
Language: English
Status: Completed
Published: 2015-08-25
Updated: 2015-08-25
Packaged: 2018-04-17 05:24:23
Rating: Teen And Up Audiences
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 1
Words: 8,169
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/4653966
Author URL: https://archiveofourown.org/users/caranfindel/pseuds/caranfindel
Summary: <blockquote class="userstuff">
              <p>Sure, he can spout a lot of brave talk about Team Free Will, but he knows the truth: you try to buck destiny, and you find that instead of killing your brother, you're setting up the dominos that eventually knock him into the Pit as Lucifer's eternal meat suit, and how is <i>that</i> a win? One way or another, destiny has its way with you and there's not a single fucking thing you can do about it, at least in Dean's experience. So he knows what to expect here.</p>
<p>Or, Dean deals with the implications of Cain's prophecy.</p>
            </blockquote>





	I'll tell you my sins and you can sharpen your knife

**Author's Note:**

> Fills the non-linearity square on my [Bingo card](caranfindel.livejournal.com/48734.html) for [Spnspiration.](spnspiration.livejournal.com)
> 
>  
> 
> I started writing this after Dean killed Cain, and there was a lot we didn't know about the Mark. I decided not to post it back then because, as the charming and astute [Frozen_delight](http://archiveofourown.org/users/frozen_delight/pseuds/frozen_delight) pointed out, everything I thought I knew about the Mark was wrong. ;-) And after the season finale I thought about reworking it to make it canon-compliant and decided I liked it better the way it was. So, consider this an AU. And forget everything you know about the Mark of Cain except for these things: it turns you into a demon if you're killed, it eventually turns you into a demon even if you're not killed, and it makes it difficult or impossible to kill you.

__  
**before**  


The thing is, Dean's been on this side of a prophecy before. He is, after all, the Righteous Man. The Michael Sword. He knows how useless it is to fight it. Sure, he can spout a lot of brave talk about Team Free Will, but he knows the truth: you try to buck destiny, and you find that instead of killing your brother, you're setting up the dominos that eventually knock him into the Pit as Lucifer's eternal meat suit, and how is _that_ a win? One way or another, destiny has its way with you and there's not a single fucking thing you can do about it, at least in Dean's experience. So he knows what to expect here. And it takes several months, but Cain's prediction eventually comes to fruition, and Crowley is the first domino to fall. 

And yes, Dean does have mixed feelings about it. He doesn't miss the demon. Crowley had occasionally been helpful, but he was still an enemy, a thorn in Dean's side, an ugly reminder of a time Dean would prefer to forget. But objectively (for those capable of thinking objectively), it's not in their best interests to kill him. Having a frenemy as the King of Hell can only work in their favor. Someone who seems to enjoy having an excuse to work with them, who has skirted the fringes of humanity recently? Anyone can see it's better to have that guy as the ruler in Hell instead of someone who quite simply wants them dead and has the resources to make it so. 

But Dean isn't thinking about any of that when it happens. When it happens, as he stands bowed in pain and fatigue, heaving ragged breaths over Crowley's empty husk, waiting for the red haze of fury to clear from his vision, waiting for his pulse to stop chanting _kill him kill him kill him_ , he doesn't think about any of that. At the time, all he can do is look at Sam and Cas, look at the horror and sadness written on their faces, and think, _oh, fuck me, here we go._

Sam actually outdrinks Dean once they get back to the bunker, and Dean wonders if it's in celebration or mourning, if he's self-medicating for insomnia or depression or some secret pain Dean's not aware of, and he feels like he should ask, should point out how unhelpful it is, but, yeah. Pot, meet kettle, and all that. Whatever. 

After he leads Sam to bed, with his little brother drunkenly trying to reassure him that everything is okay now and everything will be okay in the future, Dean finds Cas making coffee in the kitchen. He ignores the coffee and pours his own dose of medicine instead, aware that Cas is watching him the way he does when he's getting ready to say something Dean won't want to hear. Dean ignores him, the way he does when hopes Cas will change his mind and not say it. 

Cas always wins. 

"I heard what Cain said to you," he finally says. "When he told you what would happen after you killed him. That you would kill Crowley next." 

"You heard that? Does Sam know?" 

"I haven't discussed it with Sam." Cas shakes his head gravely. "I have no reason to believe he knows." 

"Good. Don't tell him." Sam's been preternaturally calm ever since Cain, but Dean recognizes that kind of calm. It's the kind that comes from ignoring every possible outcome except the one you want. It's the calm before you chug gallons of demon blood and say yes to Lucifer and believe it's going to work simply because you cannot allow yourself to contemplate what will happen if it doesn't. Sam's calm is as brittle and fragile as a tooth that's decayed from the inside, and one slight blow will shatter him and expose the raw nerve. 

"So, I guess you know who comes next," Dean says, very deliberately not meeting Cas's eyes. 

"I know who Cain _said_ comes next. But that doesn't have to happen. You've defied fate before. Cain's prophecy doesn't mean any more than Michael's." 

No, it doesn't. But it doesn't mean any less, either. Dean looks at Cas and tries to imagine ending him, and part of him knows he'd never do it, knows he'd end himself first. But another part remembers how it felt, the loss of control, the trembling hands, the _need_ to kill something, the way he felt it crawling under his skin and gnawing at his bones. Remembers the bruises on Charlie's face and how _good_ and _right_ it felt to put them there, and wonders how far he would have gone if Sam hadn't stopped him. 

(And still another part remembers a threatening phone call and Sam's grunt of pain and his own complete indifference to it, and then the swing of a hammer and no, _no,_ stop, don't go there. And he knows that was different, he knows he isn't a demon now, but how close is he? How thin is the line between Mark and demon? How much demon was left in him when he wielded that hammer? 

Why is he afraid to look in a mirror sometimes? What does he think he's going to see?) 

He pours another drink, and the bottle doesn't chatter nervously against the glass. His hands are steady, for now. 

"Does the drinking help?" Cas asks. 

Dean shrugs. "A little." But not really. It numbs everything a tiny bit, but the only thing that helped, the only thing that eased the raging need and the incessant pounding in his brain, that silenced the voices and quieted the trembling, was stabbing Crowley, watching him dissolve in a bright burst of flame. And he knows it will wear off. Soon. 

"If I need to be stopped," he says. "If it gets to that point. _When_ it gets to that point. I need to know you'll do it." 

"Dean - " 

"No, Cas. I mean it. I need to know I can count on you. Sam can't do it. I mean, even if he would, which he won't, he can't. He can't kill me as long as I have the Mark. But an angel, with an angel blade, I know that will work." 

"Yes, it would kill you," Cas says. "And the Mark would bring you back as a demon, just as it did before." 

"And then you'd have to kill me again. I'm serious. No more demon cures. I'm too dangerous. You gotta promise, Cas, you gotta promise me that when I can't control it any more, or when the Mark turns me into a demon anyway, you gotta take your angel blade and fucking end it. Please, man. Before I hurt someone." _(Before I kill someone. Before I fulfill Cain's prophecy.)_

Castiel looks away. "All right. I will not allow you to hurt anyone," he says solemnly. 

It's not until later that Dean thinks about what Cas _didn't_ say. 

_**after**_

By the time Castiel makes it back to the bunker, Dean has warded it so heavily against angels that he shouldn't even be able to touch the front door. Dean isn't surprised to receive a text from him instead of a phone call. After the last call, after his drunken, sobbing confession _(nonoDeannoplease)_ , there's no reason Cas would want to speak to him if he didn't have to. 

_I'm here but I can't come in_

Dean replies as quickly as he can, considering that he's been drinking ever since... that. Ever since _that_ happened. 

_are u here to kill me_

His phone is silent for a few minutes, and he pictures Cas staring at the text, eyes narrowed, head tilted. Maybe he didn't make himself clear enough. 

_because i can meet u outside if that's why ur here_

And now Cas gets it, and his response is immediate. 

_NO I am not here to kill you_

Dean sighs and rubs a hand down his face, and he doesn't know why he's surprised, because of course Cas isn't going to live up to his word. Of course Cas doesn't get it, doesn't understand why it's necessary. But he asks anyway. 

_why not_

_u told me u would when it was time_

_please i need u to do this, i can't_

_(I know I can't. I tried.)_

Apparently the feathery asshole has to think about this one, because Dean has drained the dregs of his whiskey bottle before his phone blinks with a reply. 

_I promised Sam I wouldn't_

Well, that's a crappy excuse, isn't it? Because promises to Sam are so easily broken. 

_(As long as I'm around, nothing bad is gonna happen to you.)_

_(No, no, Dean, no, please.)_

The phone trembles in his hand as he types. _can u bring him back?_ He stares at the screen. _(Please, God, please say yes. Please make all of this go away. Please undo it.)_ But he knows what the answer will be. 

_I'm sorry. You know I can't do that._

Dean buries his head in his arms and sobs, a wordless wailing howl of despair. 

"Dean?" Castiel's voice barely carries through the heavy door, and suddenly Dean remembers - super fantastic angel hearing. Cas doesn't have the power to fix anything, but he sure as hell can hear it all falling apart. Isn't _that_ helpful. 

"Go away, Cas!" Dean shouts. 

Dean has no superpowers beyond an inhuman ability to fuck things up, and he can't understand Castiel's muffled reply, but the text comes quickly after. _We need to talk._

There's nothing left to talk about. Dean thinks about scrawling the banishing sigil on the door and wonders if it would work, wonders if the damn thing can reach through this thick metal door and fling Cas into the unknown. But it doesn't matter. Whether Cas is inches away or miles, he's lost to Dean forever, as lost as Sam is, separated by Dean's sins, his fuckups, his relentlessly stupid decisions, by a million things more solid, more impenetrable than the bunker door. 

_**before**_

"Shoulda run when you had the chance, Sam." 

Dean steps closer. He's in no hurry - Sam is cornered without any chance of escape. He can draw this out if he wants. And yeah, he thinks he wants. 

"You don't have to do this," Sam pleads. "You can stop it. This isn't you." 

"Isn't it?" Dean grins. "Cause I think it is. I think it's more _me_ than I've ever been." Closer still. Close enough to smell sweat and fear, to hear Sam's panicky heartbeat galloping like a prey animal. Close enough to grab a fistful of hair and yank his head back, exposing the long line of his throat. 

"Please, Dean," he whispers. 

"Sammy, Sammy, Sammy," Dean says. "I'm just giving you what you always wanted. You wanted out? Here's your out." He draws the Blade across Sam's jugular in one swift motion, and Sam is gasping for air, choking on the blood bubbling up out of his throat, his eyes still open and locked on Dean's, pleading. Like he still thinks Dean can fix it. The blood flows over Dean's hand, oozing between his fingers, coating his hand and the Blade, warm and slick and _fuck,_ it feels so good. So good. 

When Dean wakes, he can still feel Sam's body going limp and heavy in his grasp, and he spends the rest of the day trying to forget the image of Sam's half-closed eyes still fixed on his. 

_**after**_

Dean wakes with a start, with Sam's _No, no, Dean, no, please_ still echoing in his mind. He reaches for the phone, but his hand is trembling so badly he can barely hold it. He puts it on the bed and taps out a shaky message. 

_you gotta help me or else i'm going to kill someone._ He makes his way through half a bottle of whiskey before Castiel's response comes. 

_There is a demon in Sioux Falls who used to work for Crowley. He's been watching Sheriff Mills. He lives in a motel downtown, across from the library. Room 15._

If you need to kill someone, kill him. 

Fuck you, Cas. 

_not exactly what i had in mind_

_I know what you had in mind and I still won't do it. If you need to kill someone, kill this demon._

Huh. Could it be that simple? Go kill a bad guy, take the edge off? Dean has to admit, he feels better just thinking about it. He can't hunt like he used to. He can't be around people, can't interview witnesses, can't trust himself around innocents. 

_(No, no, Dean, no, please.)_

But he can do this. If Cas can just hand him the name of someone, something that needs to die. Maybe it will work. At least until Dean can convince him that _he's_ the someone, something that needs to die. 

_**before**_

Sometimes the Mark whispers, sometimes it screams. Sometimes it speaks in voices stolen from those Dean respected and feared; from his father, from Death, because when they told him Sam had to die, he said yes, he promised it would be done, and they have not forgotten. Sometimes it speaks in Alastair's voice, dark and slippery, promising an end if he'll just say yes, if he'll just stop fighting. Sometimes it's the voice of Cain, soft and powerful, reminding him that there's not a damn thing he can do to alter the course he's on. Sometimes it sounds like the agonized cries of every soul he tortured in Hell. Sometimes it's not even a sound, it's just a vibration, deep in his very core. 

Today it's the sound of his own heartbeat, quietly insinuating itself into Dean's subconscious as he stares at the ceiling above his bed, pulsing _kill them, kill them._

It doesn't stop when Sam gently raps on the door of his room, but he manages to shove it into the back of his consciousness. 

"Dean?" Sam opens the door a crack. "You awake?" 

_(Translation: You sober enough to speak English? You drunk enough not to bite my head off?)_

"Yeah, I'm awake," Dean groans, as if he'd been napping. "What's up?" 

The door opens all the way and Sam tentatively enters, peering at Dean in the dim light. "Sorry to bother you, man. I'm just looking for a book. I thought you might have had it in here when you were..." _(When you were researching the Mark. When you were trying. When you still had hope. When your life didn't seem as completely and irreversibly fucked-up as it does now. All of the above.)_ Sam uses his phone as a flashlight to examine a pile of books pushed into the corner. "You mind if I take these? Are you done with them?" 

Dean sighs. _(So done. You have no idea.)_ "There's nothing in there, Sam." 

"Yeah, okay, but still, I just thought I'd, you know. Can't hurt." Sam stammers anxiously as he gathers the books in his arms, and Dean is simultaneously annoyed by, and grateful for, the persistent little shit. 

But as Sam slides apologetically out of the room and the door clicks softly behind him, the angry thrum of Dean's heartbeat resumes. 

_**after**_

Dean wanders through the bunker, through long, dark, silent hallways. He finds Sam in the kitchen, poking at the coffee maker, still wearing the grey t-shirt he was wearing that night. 

"Sammy?" 

Sam turns and smiles fondly, as if his shirt wasn't dark with blood, as if Dean wasn't a monster at all. "Hey, Dean," he says. "What's wrong with the coffee maker?" 

"I, um. I may have thrown it against the wall." 

"Sounds like you," Sam laughs. "How's it going?" 

_(Peachy. I've done something really fucking awful and I don't know how much longer I can live with it. But I can't kill myself. How about you?)_

"Not very well, honestly," Dean says. "Sam, I'm so sorry." 

Sam rubs his neck; his palm comes away bloody. He examines it for a few seconds and looks back at Dean. "I know you are," he says kindly. "It's okay." 

"It's not. It's really not." 

His brother sighs. "You're right; it's not okay at all. I was just trying to make you feel better. I mean, you really fucked it up, didn't you?" 

He holds up a hand to silence whatever Dean was going to say, and if the hand itself didn't leave him speechless, the blood on his palm would. "No, no, stop. I'm sorry. Forget I said that. Let's start over. How are you doing? Are you dealing with the Mark okay? Does it help when Cas sends you on hunts?" 

"A little bit. I mean, I've still got to stay on lockdown otherwise. Don't trust myself around people. And it doesn't last very long." Dean wants to look at Sam, wants to remember him like this, and not... Not any other way. But the blood; he can't tear his eyes away from the blood. "Hey, Sammy?" he asks tentatively. "Is there anything you can do about...?" He waves his hand at Sam's blood-splattered shirt. 

Sam thoughtfully examines his blood-smeared hand again before wiping it on his shirt, which helps neither his shirt nor his hand. "I guess not. Sorry. Could be worse, though." 

"Jesus, Sam. How? How could it be any worse?" 

"Oh, there's always a worse." Sam gives him that affectionate smile again, the fond smile above the bloodstained throat, and it makes Dean's heart stop. Sam looks down and lightly runs his finger over the crimson splotches on his shirt. "It's not all mine, you know." 

_(No, it's not, because Sam fought back, and that doesn't make it any better.)_

"I'm sorry, Sammy." 

"I know you are," he says. "How's everything else? Are you eating?" 

"Uh, yeah. Yeah, I'm eating. Cas leaves me food." _(But it tastes like dust and I'm never hungry anyway and it scares me, Christ, it scares me, because I remember what it means.)_

"Okay," Sam nods. "So, ah. Listen. If there was something you could do to make it right, would you? Would you be willing to do that?" 

"Yes. You know I would." 

"Even if it was something you really didn't want to do?" 

"Anything. I swear. I would do anything you asked." 

"Okay. Good. I'm not here to make you feel bad. I just wanted to say, when you're ready, I'm ready. Just let me know." 

Dean frowns. "When I'm ready for what?" 

"I think you know." 

"No, Sam. I don't." 

Sam smiles. "It's okay. You will. And when you figure it out, I'll be waiting for you." 

Later, when Dean is savoring the memory of Sam smiling fondly at him and not struggling, not screaming "no," he thinks maybe there _is_ some version of events where Sam forgives him. And maybe he does have it figured out, after all. 

_**before**_

Dean stands alone in the bunker, panting, glazed with sweat. He's holding the First Blade and his hand is perfectly still, even though his heart is lurching, even though the air is thick with the coppery smell of blood and violence, even though a sob is caught in his throat; his hand is sticky with drying blood and perfectly, eerily, still. 

Castiel's vessel is on the floor in front of him. His throat is slashed, his arms and hands are sliced open with defensive wounds, and his dull blue eyes stare up at nothing. A pattern of charcoal wings stretches out across the cold tile, framing his motionless form. 

There's a low gurgling sound to Dean's right. He turns to see Sam face down on the floor, hands and feet twitching as if he's trying to crawl away from something, blood sluggishly flowing from a gaping wound between his shoulders. _Stabbed you in the back. You shoulda seen that one coming, Sammy._ As he watches, Sam goes silent and still. 

Yes, this is what it's like to be a full-blown monster. This feels familiar. 

"Dean? Are you listening to me? You've been up almost 24 hours. You should get some rest." 

Dean's vision clears at the sound of Cas's voice. He rubs his eyes and tries to get his bearings, but sitting here in the softly lit library with a very much alive Castiel is disorienting and wrong, and suddenly he's so goddamn angry, and his shaking is getting worse, and _fuck,_ he can't even be in the same room with Cas without wanting to slice him open, slice him the fuck open and just _make him stop,_ make everything stop. 

_No._

Dean lurches to his feet. "I'm sorry, Cas," he says, as he stumbles out of the library. "I can't do this." 

He collapses into his room and sits curled on the edge of his bed, with his head on his knees and his trembling fingers laced together over his neck. _(Not happening. Didn't happen, not going to happen. Make it stop, make it stop.)_ He takes a swig from the ever-present whiskey bottle next to his bed. 

"Dean." 

"Shit, Cas. You can't be in here." _(You can't be near me. You're not safe.)_

"Dean, you _can_ do this, if you'll let us help." 

"There's nothing you can do to help, Cas!" Dean shouts, hurling the bottle across the room. The only thing he can do now is get everyone he cares about out of the blast zone. He pushes himself off the bed and reaches for his duffle. 

Cas frowns at the bag. "I don't think you should leave. You shouldn't be alone." 

Dean's not going anywhere. He needs to be _here,_ with a dungeon and handcuffs, where he can be contained. He pulls the angel blade out of the depths of his bag. It's not the same as the First Blade, not even close, but he imagines thrusting it into the angel's chest, watching the light of his grace bleed around the edges, watching his eyes flame out and then dim forever, and he wants it, he wants it so goddamn much. 

He releases his grip and the blade falls from his shaking hand, landing with a metallic clatter. 

"Take it," he says, his voice rough and strained. "Take that and get out of here." 

Cas's eyes don't leave Dean's face as he bends to retrieve the angel blade. "I'm not leaving you, Dean. You need help. You can't fight this alone." 

Dean takes a deep breath and tries to silence the voice _(kill him kill him)_ , tries to erase the image of scarlet splattered across a white shirt. He picks up a chunk of the broken bottle, curved like a scimitar, and runs the glass across his open hand. Dipping a finger into his bloody palm, he begins drawing the angel banishing sigil on his wall. 

Cas is shouting, like saying the same thing louder is going to make a difference. "I told you, I don't want to leave you!" 

"I'm not giving you a choice. If you stay here, I'm going to kill you." 

Cas steps closer and reaches for his hand. "And who are you going to kill if I'm gone?" 

But he's too late. "No one, I hope," Dean says, as he slaps his hand on the completed sigil and Cas disappears in a flash of light. 

He stands there for a minute, trying to figure out what the hell he should do now. Sam's not safe as long as he's here. He made it clear that he won't kill Dean, even if it means saving his own life, even if Dean isn't really Dean. 

_(And it also became clear, didn't it, how little it takes to push Dean over the edge, to get him to a point where he will gleefully kill his little brother. How close is he to that point now?)_

And as Dean heads down the hall toward Sam's room, trying not to remember the weight of the hammer in his hand, the Mark isn't whispering. It's screaming. 

_**after**_

Since that night, the night it happened, Dean's communication with Cas has been strictly through text messages. But now, the morning after his dream of Sam, the first dream of Sam that wasn't _terror blood betrayal no noDeannoplease,_ he closes his eyes and prays. 

_Cas, I'm sorry. I fucked everything up and I know it's my fault and I know I can't undo it. But I want to fix what I can, and I need your help. I can't do it without you, man. Please._

His phone rings almost immediately, as if the angel had been waiting for him. 

"Cas?" Dean's voice is rough from disuse, and he tries (and fails) to remember the last time he actually spoke to somebody. 

"Dean." 

There's an uncomfortable pause. "So, uh." _(Jesus, Cas. Don't make this any easier on me.)_ "So you heard me. And you know what I have to do." 

"Are you sure?" Cas asks gently. So much more gently than Dean deserves, and he's so thankful for that, he has to stop and catch his breath. 

"I'm sure. I'm done, man. And I know it's not about me. I know what I want is the last thing that matters. But I've got to end this. I've got to make it right." No, he can never make it right. But he can make it as close to right as possible. 

"Okay," says Cas. "I'll see you tomorrow?" 

"Yeah," Dean says, his mouth suddenly gone dry. "Tomorrow. Thanks, Cas." 

_**before**_

Dean quietly opens the door to Sam's room. Sam will understand. Sam can lock him up and go someplace safe and it will be okay. Everything will be okay. 

His brother doesn't stir, doesn't open his eyes as the dim rectangle of light from the hallway touches his face. He looks vulnerable and helpless, and it makes something flare inside of Dean, something heated and violent and angry. 

"Sam. _Sam._ " 

Sam's eyes snap open, but they show concern, not fear, and that's just not going to cut it. _(Concern for my welfare isn't going to keep you alive, Sammy. Worrying about me won't protect you.)_

"Dean? Are you okay?" 

"I'm fine." 

"What are you doing?" Sam asks as he sits up, leaning against his headboard. 

"Cas is gone. We need to talk." 

"Gone? He left? Why? What's going on?" 

Dean holds up his bloodied palm. _"Gone_ gone. I sent him away." 

_(And who are you going to kill if I'm gone?)_

"What the fuck, Dean?" Sam gasps. "You banished him? Why?" 

_(Because it was the only way to save him. And I thought it would be the only way to save you. But it won't. It won't save you, because you won't run, and I can't make you go away, and you're just going to stay here and try to rescue me and I'll end up fucking killing you and god, Sam, please. Please don't let me do this.)_

"Because of _this,_ " Dean rasps through clenched teeth, waving his arms to encompass Sam, everything, all of it. "Because you're not even _trying_ to protect yourself. Because you didn't even wake up when I came in here." _(Because I'm going to kill you, and you're not afraid, and you're not going to stop me.)_

He snakes his hand under Sam's pillow and grabs the knife he knew would be there, the knife Sam hasn't even bothered to reach for. It's the demon knife, and for a second it's almost enough to undo him, the fact that Sam chose the fucking _demon_ knife to protect him against whatever, _whoever,_ might sneak into his bedroom, but then he's just angry, because goddammit, Sam. Dean doesn't have to be a demon to kill him. He just has to be out of control, and he's teetering on the edge, staring into the abyss right now. He waves the knife in Sam's face. "What's the point, Sam? What's the point of this knife? You understand this can't kill me, right?" 

Sam backs up as far as he can, trying to push himself into the headboard, melt into the wall. "I don't care. I won't kill you, Dean." 

"That's the fucking problem!" Dean shouts, and something in him breaks; something that was holding him together snaps like an overstretched rubber band. He pounces on top of Sam, pushing an arm against his throat and straddling his legs. Sam kicks and tries to push him off, but his legs are tangled in the covers and he can't get leverage, and Dean's leaning all of his weight against him. "That's always going to be the fucking problem," Dean growls. "You're never going to be able to kill me when you need to." Dean's still-bleeding palm leaves a crimson handprint on Sam's shoulder, and it seems to have its own voice, chanting in harmony with the voice of the Mark. 

_(But Sam's not completely wrong, is he? If he kills Dean, the Mark will bring him back as a demon. There needs to be a more permanent solution.)_

Sam's afraid now, he's fucking terrified, eyes wide as he tries to twist out of Dean's grip, but it's too goddamn late. Dean presses the knife to his brother's throat and he stills. "Sam." He gets his breathing under control. Tries to sound calm. Tries to sound like John, because this is Sam's last hunting lesson. "We only know of two things that have killed someone with the Mark, Sam. Do you remember what they are?" 

Sam swallows hard. "The First Blade," he says, almost whispering, his throat bobbing against the knife. 

"And?" Dean pushes the knife harder against his throat, watches him wince as it breaks the skin. He has to force himself to look away from the blood and train his eyes on Sam's face. "Think, Sam. You know the answer to this." 

"An angel blade. Metatron." Sam closes his eyes and draws in a deep breath. "Metatron killed you with an angel blade." 

"Very good. Now look at me, Sammy. This is important." Sam opens his eyes as Dean eases the pressure of the knife. "Cas already hid the First Blade from me. And I sent him away with our angel blade. There's nothing in the bunker that can kill someone with the Mark." 

Sam's eyes are pleading. "You didn't have to do that," he says, in that soft, steady, _sane person speaking to a madman_ voice. "I don't want to kill you." 

"I know," Dean says. "But _I_ want to kill _you._ And don't bother telling me I can fight it," he adds quickly, as Sam's mouth opens, probably to say exactly that, because Sam's pointless, doomed, unfounded faith in Dean is not going to quit. "I've been fighting it as long as I can, and I just can't fucking do it any more. But it's okay. I know how to save you." Without moving the knife from Sam's throat, he switches his grip to hold it in his left hand, and uses his free right hand to grasp his brother's hand. "If there _is_ anything else that will kill someone with the Mark, I don't know what it is, and I promise I'll never look for it. So you'll be safe. Do you understand?" 

And Sam finally does understand. "Oh, no, God, no," he says softly, as Dean's arm begins to glow. Then he's a tiger, kicking and pitching and bucking under Dean's weight, scraping his own throat bloody as Dean relentlessly presses the knife against it. Dean keeps his grip, pushing with his mind, watching the glow on his arm move toward Sam. His brother writhes under his grasp. "Stop!" he screams. "No, no, Dean, no, please!" 

They tumble off the bed as Sam tries to release himself, punching Dean in the face with his free hand, scratching and slicing both of them as the knife is trapped between them. He's finally able to break Dean's grip, kicking him in the gut, leaving him flat on his back. Sam backs away until he's against the wall, but it's too late - the angry red scar of the Mark is indelibly traced on his arm, as red as the bloodstains on his shirt. He stares at it in horror. 

"It's okay," Dean pants at the ceiling, as he tries to catch his breath. "I can't kill you now." 

Sam leans motionless against the wall for several minutes, eyes closed, chest heaving, blood from his raw-scraped throat seeping into the neckline of his t-shirt. Then, without a word, he gets up, steps over Dean, and starts throwing clothes into his duffle. Ten minutes later, when the bunker door closes behind him, he still hasn't spoken a word, and Dean hasn't moved. 

"I'm sorry," Dean says to the silent ceiling, the blood-flecked bed, the empty room. "I did what I had to do." 

_**after**_

They're not quite an hour away from the bunker when Cas turns onto a rutted dirt road. Dean follows him for a couple of miles, almost losing Cas's car in the cloud of dust it raises, before he turns into an even more severely rutted driveway. 

The little farmhouse at the end of the driveway looks peaceful enough. The wide porch is shaded by a couple of gnarled apple trees and overlooks a small, tidy garden. It reminds him of Cain's little house - all it needs is bees - but really, it could be anyone's homestead. Anyone, that is, who'd go to the trouble of having a satellite dish installed to get an internet signal. Dean smiles. Some things never change. 

The screen door opens and Dean swallows hard. In some ways, Sam looks exactly as he did the last time he saw him (and he suddenly can't remember whether that was five months ago, or five years, or five lifetimes). In other ways, he looks infinitely older. 

Sam nods briefly at Cas and watches him circle through the yard and head back down the long driveway. Then he steps off the porch as Dean gets out of the Impala, and he looks as nervous as Dean feels. 

His eyes. It's his eyes that look older. His face is the same, his gait is the same, the way he anxiously pushes his hair behind his ears is the same, but his eyes are haunted, as if centuries in Hell finally caught up with him. 

Dean swallows again. "I'm sorry, Sam." 

"I don't care." 

Well, that stings, but Dean can't say he doesn't deserve it. "Please, man, just hear me out." 

Sam shakes his head and smiles. "No, I mean, I don't care any more." He takes a few more steps and folds Dean in an embrace. "I don't care about any of it," he repeats into Dean's neck. "God, Dean. I really, really don't." 

Okay then. The tension that's been holding Dean upright falls away and he wraps his arms around his giant little brother, swaying back and forth as if he were trying to comfort little Sammy again, and when the Mark begins to whisper about circling his hands around Sam's throat, he's able to push it almost completely into his subconscious. 

Finally Sam pulls away. "So, um. Cas said he wouldn't bring you unless..." 

"Yeah. I know. I'm ready." 

"Okay." Sam sighs. "Okay. Good." 

"But not just yet, okay?" 

"No. No, of course not." Sam turns and leads him into the house. 

Something about the little farmhouse makes Dean twitchy. Or maybe it's his proximity to Sam. Either way, the Mark is thrumming insistently as Dean surveys the house. It's sparsely furnished, with a couch and coffee table in the front room, an almost-bare bedroom, and a small kitchen and bathroom. Sam takes a couple of beers out of the ancient refrigerator and motions Dean toward the couch. The coffee table is empty except for Sam's laptop, which he opens and turns toward Dean. "I want to show you what I've been working on." 

_Working on._ Of course, while Dean has spent their time apart grieving and moping and drinking and slowly going batshit crazy, Sam's been _working on_ something. 

"It's a monster wiki. For hunters. See, everything we know is online now. Well, not all the Men of Letters stuff. This is just monsters and demons, not angels and the really serious shit. Cas and I decided we don't want to encourage people to fight those battles." 

"Jesus, Sam. This is impressive. This is a lot of work here." 

"Keeps me occupied," Sam shrugs. "Keeps me sane." He rubs his arm absently, and Dean has a very sudden and violent reminder of just why Sam needs to be kept occupied, and why he needs help staying sane. 

"That's great." 

Sam stares at him for a moment, then looks away and laughs darkly. "Yeah, it's great." He leans back into the couch and runs his hands down his face. "Listen. I'm not trying to kick you when you're down or anything, but nothing about this is _great._ I'm not exactly writing a book on how to live successfully with the Mark of Cain. I'm surviving. On good days I work on the wiki and I work in my garden and sometimes Cas brings me supplies and we talk. And on bad days, I'm practically hiding under the bed." He brandishes his Marked arm. "Because this thing is my own little personal gateway to Hell, and it talks to me, Dean. It talks to me and it has Lucifer's voice." 

_Jesus fuck._ Dean stands up and walks to the window. He can't look at Sam right now, can't face what he's done to him. 

"It's amping up the volume now that you're here," Sam continues softly. "Yours is too, isn't it?" 

Dean chooses not to confirm that the Mark is reminding him that he wants to feel his brother's blood on his hands, to rip his throat out with his teeth, to swing a hammer into his skull. "I'm sorry, Sam," he says, still facing out the window. "I thought I could save you." 

"But you know you didn't really save me, right? You understand it would have been better for _me_ if you'd killed me, right?" 

He leans into the window, resting his forehead against the cool glass. Outside the grass is still soft and green, not yet crisped by the Kansas summer, and he notices a low ridge spanning the yard. He traces it with his eyes - it circles the little house, with spurs going off in different directions, and peculiar yet familiar patterns, and he suddenly recognizes it. 

"Sam? Is this house in the middle of a giant devil's trap?" 

"Iron pipe, a couple of inches underground," Sam says behind him. "Filled with rock salt." 

"Shit." 

In another life, he would have made a joke about Sam expecting a demon invasion. But in this life, or what's left of it, he knows this trap isn't meant to keep anything _out._

And yes, he also knows he didn't save Sam from anything. His last, most selfish act was to once again condemn Sam to Hell because he couldn't face the thought of being the one to give him death instead. 

"So, are you gonna help me with this thing?" 

Dean turns around and Sam's sitting on the couch, smiling fondly, just like his dream. 

"Seriously?" 

"Yes, seriously. We need to finish the entry on the Mark of Cain." 

And once again, Sam forgives him, because apparently that's what Dean spent decades training him to do. He should feel guilty about that, but he doesn't. "Okay, geek boy," he grins. It's been so long since he grinned that he's nearly forgotten how, and they're almost okay. Almost normal. "If you're in a hurry." 

Sam turns to the laptop, not meeting Dean's eyes. "Oh, you know. Miles to go before I sleep, and all that." 

Yeah, that. Dean decides to ignore it for now and examines the menu to Sam's wiki instead. "Where'd you get all this info? You had it memorized?" 

"Some of it. But I used Dad's journal, too." 

"You had Dad's journal?" 

Sam looks guilty, and Dean feels a momentary flash of anger. _Dammit, Sam, he was your father too. You have just as much right to it as I do._

"It was in my bag when I left. From that last hunt. I'm sorry; were you looking for it?" 

"No, no. I wasn't... I haven't... I'm not hunting, Sam. I'm just. Executing, I guess. Cas sends me the info and I take them out. That's really all I can do." 

"And it's still working? You said it didn't last as long as it did before." 

"Yeah, it doesn't work like it used to," Dean muses. He pauses and waits for something to coalesce in his brain. "Wait. How did you know that? What do you mean, I said?" 

Sam looks down and smiles. "You told me." 

_There_ it is. "Dreamroot? You dreamwalked me, you little shit?" 

Sam throws back his head and laughs, and anything, _anything_ he might have done is worth it. "I'm sorry," he says. Except he's clearly not. "I needed to talk to you, and I had your blood on my shirt, so..." 

"So you got my DNA out of it and you fucking dreamwalked me. That's, just, that's so inappropriate. _Boundaries,_ Sam." But he's laughing, and Sam's laughing, and it all feels so right, and of course that means it can't last, but for now he's going to enjoy it. 

He goes through Sam's wiki and makes a few changes, adds a few things Sam missed or forgot or never knew in the first place. Sam insists that he add his name as contributor, and it feels good to leave that kind of legacy behind. 

There is no wiki entry on Dean Winchester. Hunter, brother, eternal fuck up, Righteous Man, Michael Sword, bearer of the Mark of Cain and all that implies. Or Sam Winchester, Lucifer's vessel and conqueror. Some things just don't need to be put in writing. 

They talk and drink and laugh and drink some more, and it's practically normal. Almost like old times. But eventually Sam grows quiet and Dean knows it's time to do what he came here for, to undo that last, most selfish act. 

... 

"There's a spell," Sam says. "It doesn't get rid of the Mark, but it does stop... it stops a person from turning into a demon when they're killed." He's gathered some materials into a bowl - plants Dean recognizes, plants he doesn't, words in a script he can't read scrawled on something that looks more like skin than paper, small bits of things he chooses not to examine too closely. 

"And this spell comes from...?" 

Sam gives him a weary smile. "Just trust me, okay? I'm not asking you to trust anyone else. Trust me on this one. Please." He pulls out a flask of holy water and dribbles some into the bowl. "And if it doesn't work," he adds, "Cas knows what to do." He takes a knife out of his pocket and draws a shallow cut along his arm, holding it over the bowl, then offers the knife to Dean. "I can't do it without your help. But, you know, that's just for me. If you're not ready... if you don't want to do it too... I understand." 

_Want_ isn't exactly the word Dean would use, but Sam's not doing this without him. He accepts the knife and adds his own blood to the bowl. Sam uses a peeled stick to stir the ingredients into a paste, muttering an incantation in a language Dean doesn't recognize. He rolls up his sleeve and smears a little of the paste on his arm, over the Mark, then motions to Dean to do the same. When the mixture touches the Mark, it flares slightly in anger, its voice growing more strident. 

As the sun sets, Sam takes a couple of bottles from the fridge, retrieves a long wooden box from the kitchen, and nods his head toward the door. When Dean sees the box, decorated with ancient symbols to bind, protect, and conceal, he understands why he felt so edgy when he entered the house. 

They step out into the darkness and quietly drink their last beers on the hood of the Impala, looking at the stars. 

... 

Sam's ready before Dean is. "You know _you_ have to do this part, right?" he says, handing Dean the box. "You know the Mark won't let me do it." 

Yeah. He knew that. And the fact that Sam knows it too, knows that the Mark won't let him end his own life... well, he desperately hopes he discovered it through research, and not trial and error. 

But it's one thing to say goodbye, and it's another thing to do the deed. There's a name for that deed, and it's a name Dean hoped wouldn't end up attached to him. But then again, what's the difference? Is fratricide really any worse than making your brother's life such a hellish mess that he prefers death? That death is a release, not a loss? Leave it to Dean Winchester to completely fuck up his brother's life in an attempt to keep from killing him, and then fulfill his destiny anyway. 

He opens the box and removes the soft leather that covers the First Blade, but he's not ready to touch it. Not just yet. "I'm sorry, Sam," he says, acutely aware that he could apologize all night and it wouldn't be enough. "I thought I was doing the right thing. I never wanted to hurt you." 

"I know," Sam replies. "It's okay. But I'm just kind of ready for it all to be over, now. Aren't you?" 

"Yeah, I am," and he thinks maybe he means it. Sam holds out his left arm, the Mark burning angrily beneath the smeared bloody ingredients of the spell, and for the first time, Dean notices he is trembling. "How long you been dealing with that?" 

"Just now." Sam's voice is slightly tense from some internal struggle, his hand curling into a fist. "Just since you opened the box. It's okay," he says, waving off Dean's concerned look. "I'm good." 

Dean picks up the Blade, and as the voices inside his head cry out for violence, almost completely drowning out the tiny voice that whispers _am I really doing this?_ , he slides it into the crook of Sam's elbow and draws it as gently as possible down his shaky arm, opening the vein. _(There's your fratricide, Cain. I hope you choke on it.)_

Sam hisses in pain and then visibly relaxes, as if his own internal voices are spilling out of his body along with the blood that drips through his fingers and down the hood of the Impala. Dean quickly places the Blade in his hand and Sam makes the cut along Dean's arm, slicing through the Mark. Dean understands why Sam was so shaky now; his arm trembles with the effort of holding it still, fighting the Mark's instinct to preserve itself. He pushes into the Blade, willing his wound to be deeper than Sam's, because there is no version of this story where Sam's allowed to go first. Suddenly he's struck with terror that the wound will seal itself shut and he'll be left here alone, watching Sam bleed out, and _fuck,_ why didn't he make Sam cut him first? But he must have lost his self-healing properties along with his black eyes. Dean sighs in relief as the blood flows down his arm. Sam drops the Blade over the side of the Impala, into the grass, out of sight, and it's done. They're done. 

It's over. And it's not really a bad thing after all. 

He leans back against the windshield and places his hand over Sam's, their blood pooling together. "We did good, Sammy," he says. 

Next to him, Sam stares up at the stars. "Yeah, Dean," he says, his voice soft and groggy. "We did." 

... 

Castiel returns at dawn and finds them still on the Impala, their blood mingled in a sticky dark ribbon running down its hood. Whatever it was that made these two the Winchesters is long gone, but what they left behind is still important to him. He covers them carefully with a tarp and stacks wood around the car - unnecessary for the fire, but seemingly an important part of a hunter's funeral. Before lighting the fire, he goes into the cabin and finishes Sam's last wiki entry, the entry on the Mark of Cain, confirming that the last known humans to carry the Mark are deceased. He then adds the Blade to the pile of kindling, sprinkles salt and lighter fluid over the pyre, and sets it ablaze. 

The ashes have long since cooled by the time the sun sets over the charred pyre, but Castiel stays to watch it, as he's fairly certain he won't return to Earth to watch another sunset for a very long time.


End file.
